<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        /*
        字面量：见面知义
        js的数据类型：
            1.数字型，纯数字即可。
            2.字符串，双引号、单引号。
            3.布尔值（boolean）：true  false boolean
            4.undefined   undefined
            5.null   object
        */
        var age = 18;
        console.log(typeof age);
        var address = "郑州";
        console.log(typeof address);
        console.log(typeof true);
        console.log(typeof undefined);
        console.log(typeof null);
    </script>
</body>
</html>